Producing method of film with through-holes

ABSTRACT

A film is made of an elastic material. The film is stretched in at least one direction in parallel to a surface of the film. Then, through-holes are punched in the film be means of needles, in a state the film is stretched. After the punching is completed, the stretching is terminated, so that the film recovers its original shape.

This application is a divisional of U.S. patent application Ser. No.09/161,306, filed Sep. 28, 1998, the contents of which are expresslyincorporated by reference herein in its entirety.

BACKGROUND OF THE INVENTION

This invention relates to a producing method of a film withthrough-holes.

Generally, such film is made of a plastic film. A punching machine isused to form through-holes on the film. The punching machine is arrangedto pierce the film with needles. In order to improve the accuracy ofdimensions (such as diameters and pitches) of the through-holes, it isnecessary to improve an operation accuracy of a punching machine.However, such improvement of the punching machine may increase theproducing cost of the film.

Accordingly, there is a strong demand for a producing method of a filmwith through-holes which achieves a high accuracy of the dimensions ofthe through-holes, without increasing the producing cost of the film.

Further, it is difficult to produce a film with through-holes whichinclination angles (from a direction of a thickness of the film) arerelatively large. This is because, when the film is pierced with aneedle in an inclined direction, the film tends to be bent.

Accordingly, there is a strong demand for a producing method of a filmwith through-holes which inclination angles (from a direction of athickness of the film) are relatively large.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide aproducing method of a film with through-holes, which achieve a highaccuracy of dimensions of the through-holes without increasing theproducing cost of the film.

Further, it is another object of the present invention to make itpossible to produce a producing method of a film with through-holeswhich inclination angles (from a direction of a thickness of the film)are relatively large.

According to an aspect of the present invention, there is provided amethod including the steps of (1) stretching the film in at least onedirection in parallel to a surface of the film, (2) formingthrough-holes in the film in a state the film is stretched, and (3)terminating the stretching of the film after the through-holes areformed.

After the stretching is terminated, dimensions of the film in thestretching direction decrease. Thus, error of dimensions (such asdiameters and pitches) of the through-holes of the film also decrease.As a result, the accuracy of the dimensions of the through-holes isimproved, without improving an operation accuracy (of a punching machineor the like) in the through-hole-forming step. Consequently, it ispossible to achieve a high accuracy of the dimensions of thethrough-holes of the film, without increasing the producing cost of thefilm.

In the through-hole-forming step, it is preferred to form thethrough-holes by punching. With this, the producing cost is relativelylow (compared with a laser machining or the like).

In a particular arrangement, a clamp mechanism is used in the stretchingstep. The clamp mechanism holds at least two sides of the film tostretch the film. With this, the film can be continuously stretched bymeans of a simple mechanism. Also, with such a clamp mechanism, biaxialstretching is enabled.

Further, the through-holes are formed on at least one row in thethrough-hole-forming step. With this, the produced film can be employedin an ink transfer printer described below. In such case, thethrough-holes are faced with heating elements of a thermal line head.

According to another aspect of the present invention, there is provideda producing method of a film (made of shape memory resin) withthrough-holes. The producing method includes the steps of (1) heatingthe film to a temperature above a glass transition temperature of theshape memory resin, (2) stretching the heated film in at least onedirection, (3) cooling the stretched film to a temperature below theglass transition temperature, (4) forming through-holes in the film, and(5) heating the film to a temperature above the glass transitiontemperature.

As the stretched film is cooled before the film recovers its original(non-stretched) shape, the film is solidized in a state the film isstretched. Thus, it is possible to keep the stretched state of the filmwithout continuously applying force to the film.

In a particular arrangement, a pair of heat rollers are used to heat thefilm and to stretch the film. The film is inserted in a gap between therollers and pressed therein, so that the film is stretched. Optionally,a fan is used to cool the film in the cooling step. The fan is locatedin the vicinity of the heat rollers.

According to still another aspect of the present invention, there isprovided a producing method of a film with through-holes. The film ismade of shape memory resin. The producing method includes the steps of(1) forming through-holes in the film, (2) heating the film to atemperature above a shape-providing temperature of the shape memoryresin, and (3) stretching the film in at least one direction in parallelto a surface of the film, in a state the film is heated to a temperatureabove the shape-providing temperature.

The produced film is thinner than the film in the through-hole-formingstep. Further, dimensions of the ‘produced’ film in the stretchingdirection are larger than those of the film in the through-hole-formingstep. Thus, the inclination angles of the through-holes (from adirection of a thickness of the film) of the produced film are largerthan those of the through-holes formed in the through-hole-forming step.Accordingly, it is possible to produce a film with through-holes whichinclination angles (from a direction of a thickness of the film) arerelatively large.

In a particular arrangement, a pair of rollers are used in thestretching step. The film is inserted in a gap between the rollers andpressed therein. The rollers are heated to a temperature above theshape-providing temperature.

The film produced by the above-described producing method can be used inan ink transfer printer. The ink transfer printer includes (1) a thermalhead comprising a plurality of heating elements, the thermal head beingfaced with the film so that the heating elements are faced with thethrough-holes of the film, (2) a space formed between the thermal headand the film, which holds ink therein, (3) a platen member which urges arecording media to a surface of the film. When the heating elementsselectively heat the ink in the space and the film, ink permeates thethrough-holes of the film and transferred to the recording media.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A, 1B, 1C and 1D are schematic views showing a producing methodof a film with through-holes according to a first embodiment;

FIG. 2 is a perspective view of the film of FIG. 1;

FIG. 3 is a sectional view of a ink transfer printer using the film ofFIG. 2;

FIG. 4 is an exploded perspective view showing a main part of the inktransfer printer of FIG. 3;

FIGS. 5A and 5B are schematic views illustrating ink transferringprocess;

FIG. 6 is an enlarged view of the film nipped by a thermal head and aplaten roller of the ink transfer printer of FIG. 3;

FIG. 7 is a diagram showing an example of a characteristic of a shapememory resin according to the second embodiment;

FIGS. 8A, 8B, 8C and 8D are schematic views showing a producing methodof a film with through-holes according to the second embodiment; and

FIGS. 9A, 9B, 9C and 9D are schematic views showing a producing methodof a film with through-holes according to the third embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The embodiments of the producing method of a film with through-holesaccording to the present invention are described below.

FIGS. 1A, 1B, 1C and 1D are schematic views showing a producing methodof a film with through-holes according to a first embodiment. A film 2shown in FIG. 1A is made of polytetrafluoroethylene (Teflon(trademark)). The film 2 has a square shape, each side thereof havingthe length L. The thickness t of the film 2 is from 0.03 to 0.08 mm. InFIG. 1A, X-direction and Y-direction are defined along two adjacentsides of the film 2.

As shown in FIG. 1B, the film 2 is stretched in two directions. A clampmechanism is used to stretch the film 2. The clamp mechanism has fourclamps 110 which respectively hold four sides of the film 2 (one ofclamps 110 is not shown in FIG. 1B) and stretches the film 2 inX-direction and Y-direction. The film 2 is stretched so that the lengthof each side becomes 2L, and so that the thickness of the film 2 becomest/4.

As shown in FIG. 1C, through-holes 25 are punched in the film 2 by meansof needles 115 of a punching machine. The through-holes 25 have acertain diameter D, and are arranged on two rows with a certain pitch P.The film 2 is pierced with the needle 115 in a direction that isinclined from a direction of a thickness of film 2 to Y-direction. Thatis, the through-holes 25 are inclined to Y-direction. Due to theoperation accuracy of the punching machine, error in dimensions (such asdiameters and pitches) of the through-holes 25 is approximately 0.02 mm.After the through-holes 25 are formed, the stretching of the film 2 isterminated, so that the film 2 recovers its original (non-stretched)thickness as shown in FIG. 1D. With this, the film 2 with through-holes25 is produced. The ‘produced’ film 2 is shown in FIG. 2.

As shown in FIG. 1D, since the film 2 recovers its original(non-stretched) thickness, the thickness of the film 2 changes from t/4to t. Also, the length of each side of the film 2 changes from 2L to L.Accordingly, the diameter of the through-holes 25 changes from D to D/2.Also, the pitch of the through-holes 2 changes from P to P/2.

As a result, even if the error of the dimensions of the through-holes 25is 0.02 mm in the punching step (FIG. 1C), the error of the dimensionsof the through-holes 25 of the ‘produced’ film 2 (FIG. 1D) is 0.01 mm.That is, the accuracy of the dimensions of the through-holes 25 isdoubled.

As described above, by punching the through-holes 25 in the film 2 in astate the film 2 is stretched, the accuracy of dimensions ofthrough-holes 25 can be consequently improved, without improving theoperation accuracy of the punching machine.

In the above-described first embodiment, it is possible to formthrough-holes 25 throughout the surface of the film 2. Further, it ispossible to stretch the film 2 in only one direction (instead of twodirection). In case the film 2 is stretched in Y direction, the shape ofthe through-holes 25 of the produced film 2 is ellipse that is elongatedin X direction.

An ink transfer printer using the film 2 is described. FIG. 3 is asectional view of the ink transfer printer. The ink transfer printerincludes a thermal line head 3 having multiple of heating elements 35arranged in a row. The above-described film 2 with through-holes (notshown in FIG. 3) is supported by a board 3 a of the thermal line head 3via a spacer 8 provided therebetween, so that the film 2 and the thermalline head 3 are faced with each other.

The spacer 8 and the board 3 a of the thermal line head 3 are made ofmaterials which do not allow the permeation of ink. Thus, ink is storedin a space surrounded by the spacer 8, the board 3 a of the thermal linehead 3 and the film 2. A platen roller 4 is provided at the opposingside of the film 2 with respect to the thermal line head 3, so that arecording media R is sandwiched by the platen roller 4 and the film 2.The circumferential surface of the platen roller 4 is made of rubber.The rotation shaft 4 a of the platen roller 4 is orientated in adirection in which the heating elements 35 of the thermal line head 3are arranged. When the platen roller 4 is rotated, the recording media Ris fed in the direction shown by an arrow in FIG. 3, due to a tractionbetween the recording media R and platen roller 4.

FIG. 4 is an exploded perspective view of the ink transfer printerexcept the platen roller 4. The spacer 8 is a thin plate member whichsurrounds the heating elements 35 of the thermal line head 3. That is,the spacer 8 defines four side borders of the ink space 1 in which theheating elements 35 are located. In order to supply ink to the ink space1, an ink tank 6 is provided on the board 3 a of the thermal line head 3so that the ink tank 6 is adjacent to the spacer 8. The ink tank 6 has anot-shown cavity in which ink can be stored. Ink stored in the ink tank6 is introduced into the ink space 1 through a slit-shaped outletopening 62 formed on the ink tank 6 and a slit-shaped connecting opening85 formed on the spacer 8, due to a capillary action. The film 2 isattached to the upper surface of the spacer 8 so that the through-holes25 are faced with the heating elements 35 of the thermal line head 3.

FIGS. 5A and 5B are schematic views showing an ink transferring process.As shown in FIG. 5A, the diameter of the through-holes 25 are small sothat ink does not permeate the through-holes 25. The film 2 is almost incontact with the heating element 35 of the thermal line head 3. When theheating element 35 is heated, ink located in the vicinity of the heatingelement 35 is heated. As shown in FIG. 5B, the heated ink is vaporizedand expanded, causing an increase in the local pressure of ink. Also, aportion of the film 2 located in the vicinity of the heating element 35is heated. The elastic coefficient of the heated portion of the film 2decreases, so that the heated portion of the film 2 is easily deformed.Due to the increase in the local pressure in ink, ink is pushed into thethrough-hole 25 of the film 2. Further, the through-hole 25 is widen soas to allow the permeation of ink. With this, ink permeates thethrough-hole 25 and is transferred onto the recording media R (FIG. 3)which is in contact with the upper surface of the film 2. After theheating of the heating elements 35 is stopped, the heated ink is cooledby the surrounding ink, so that the increase in the local pressure inink disappears. Further, the heated portion of the film is also cooledby ink. With this, the widened through-holes 25 recover their originaldiameters so that the through-holes 25 do not allow the permeation ofink.

As constructed above, by controlling the thermal line head 3 toselectively heat the heating elements 35 and by rotating the platenroller 4 to feed the recording media R, a desired image is formed on therecording media R.

In the above-described ink transfer printer, it is possible to arrangethat the film 2 is sandwiched by the heating elements 35 and the platenroller 4 as shown in FIG. 6. Since the through-holes 25 of the film 2 isinclined from a direction of the thickness of the film 2, thethrough-holes 25 are almost closed. With such an arrangement, even if anunintentional pressure is applied to ink (or to the film 2), anunintentional permeation of ink is prevented. Thus, the ink leakage isprevented. Further, it is possible to constitute the spacer 8 of anadhesive agent instead of the thin plate member.

The second embodiment of the present invention is described. In thesecond embodiment, a film 200 is made of shape memory resin whichexhibits different characteristics above/below a glass transitiontemperature Tg. FIG. 7 is a diagram showing an example of thecharacteristics of the shape memory resin. When the shape memory resinis heated to a temperature above a glass transition temperature Tg (andbelow a shape-providing temperature T0 described below) as shown by “b”in FIG. 7, the shape memory resin exhibits a rubber state, in whichBrownian motion of molecules is activated. When the shape memory resinis cooled to a temperature below the glass transition temperature Tg asshown by “a” in FIG. 7, the shape memory resin exhibits a solid state inwhich Brownian motion of molecules is frozen. Further, if the shapememory resin is heated to a temperature above ashape-providing-temperature T0 as shown by “c” in FIG. 7, the shapememory resin exhibits a fluidized state in which molecules arefluidized. In this fluidized state, the shape memory resin is given anoriginal shape. Examples of the shape memory resin are as follows: (1)polynorbornene, (2) trans-1,4-polyisoprene, and (3) polyurethane. Inthis embodiment, polyurethane resin (which is low cost and has excellentmoldability) is used. In this embodiment, the glass transitiontemperature Tg of the shape memory resin is from 60_C to 80_C. The shapememory resin is disclosed in Japanese Laid-Open Patent Application Nos.HEI 5-305666 and HEI 8-49960, teaching of which are incorporated byreference in their entireties.

FIGS. 8A, 8B, 8C and 8D are schematic views showing the producing methodaccording to the second embodiment. As shown in FIG. 8A, the film 200made of the shape memory resin has a thickness t of 2 mm. This film 200is inserted in a gap between two heat rollers 210. The heat rollers 210are heated at 70_C, which is higher than the glass transitiontemperature Tg of the shape memory resin. The film 200 is heated so thatthe film 200 exhibits a rubber states and pressed by the heat rollers210, so that the film 200 is stretched in one direction (referred to asY-direction). The film 200 is stretched so that the thickness of thefilm 200 is 0.05 mm (t/40). A pair of fans 220 are located at downstreamside of the heat rollers 210. The film 200 which moves out of the gapbetween the heat rollers 210 is rapidly cooled by fans 220 to atemperature below the glass transition temperature Tg. That is, the film200 is cooled just after the film 200 is stretched and before the film200 becomes thicker. With this, the film 200 exhibits the solid state ina state the film 200 is stretched.

Further, as shown in FIG. 8C, through-holes 205 are punched in the film200 by means of needles 215. The diameters of the through-holes 205 aredenoted by D in FIG. 8C. After punching of the through-holes 205, thefilm 200 is heated to a temperature above a glass transition temperatureTg by means of a heater (denoted by H′ in FIG. 8D). As a result, thefilm 200 recovers its original thickness as shown in FIG. 8D. That is,the thickness of the film 200 is changed from 0.05 mm (t/40) to 2 mm(t). The diameter of the through-holes 205 in the stretching direction(Y-direction) becomes D/40. With this, the film 200 with through-holes205 is produced.ü@The film 200 produced by the process shown in FIGS. 8Athrough 8D can be used as a film 2 in the ink transfer printer shown inFIG. 3.

As described above, even if the error in the dimensions (in Y-direction)of the through-holes 205 is 0.02 mm in the punching step (FIG. 8C), theerror in the dimensions (in Y-direction) of the through-holes of theproduced film 200 is 0.0005 mm. That is, the accuracy of thethrough-holes of the produced film 200 in Y direction is improved.Further, since the film is solidized in a state the film is stretched,it is possible to keep the stretched state of the film withoutcontinuously applying force to the film.

The third embodiment of the present invention is described. In the thirdembodiment, a film 300 is made of a shape memory resin similar to thesecond embodiment.

FIGS. 9A, 9B, 9C and 9D are schematic views showing the producingprocess according to the third embodiment. As shown in FIG. 9A, a film300 made of the shape memory resin has a thickness t of 2 mm. First, asshown in FIG. 9B, through-holes 305 are punched in the film 300 by meansof needle 315. The piercing direction of the needle 315 is inclined toone direction (referred to as Y-direction). The inclination angle of thepiercing direction of the needle 315 from a direction of the thicknessof the film 300 is denoted by (. The diameter of the through-holes 305is denoted by D in FIG. 8C.

After the through-holes 305 are formed, the film 300 is inserted in agap between two heat rollers 310 in Y-direction. The heat rollers 310are heated at 150_C, which is higher than the shape-providingtemperature T0 of the shape memory resin of the film 300. The film 300is heated so that the film 300 exhibits a rubber states and pressed bythe heat rollers 310, so that the film 300 is stretched in Y-direction.The film 300 is stretched so that the thickness of the film 300 is 0.05mm (t/40). Since the film 300 is heated to a temperature above theshape-providing temperature T0, this shape of the film 300 (having thethickness of 0.05 mm) becomes an original shape of the film 300. Withthis, the film 300 with through-holes 305 is produced. The film 300produced by the process shown in FIGS. 9A through 9D can be used as thefilm 2 in the ink transfer printer shown in FIG. 3.

As shown in FIG. 9D, the inclination angle (of the through-holes 305 ofthe ‘produced’ film 300 from a direction of the thickness of the film300 is larger than inclination angle (the piercing direction (FIG. 9B)of the needle 315. Accordingly, it is possible to form the film 300 withthrough-hole 305 which inclination angle from a direction of thethickness of the film 300 is relatively large.

Although the producing method of a film with through-holes is describedherein with respect to the preferred embodiments, many modifications andchanges can be made without departing from the spirit and scope of theinvention.

The present disclosure relates to subject matters contained in JapanesePatent Application No. HEI 09-282633, filed on Sep. 30, 1997, which isexpressly incorporated herein by reference in their entirety.

What is claimed is:
 1. A producing method of a film with through-holes,said film being made of shape memory resin, said method comprising thesteps of: forming through-holes in said film such that saidthrough-holes are inclined; heating said film to a temperature above ashape-providing temperature of said shape memory resin; and stretchingsaid film in at least one direction in parallel to a surface of saidfilm, in a state said film is heated to a temperature above saidshape-providing temperature.
 2. The producing method according to claim1, wherein said through-holes are formed on a row in saidthrough-hole-forming step.
 3. The producing method according to claim 1,wherein said through-holes are formed by punching in saidthrough-hole-forming step.
 4. A film produced by the producing methodaccording to claim
 1. 5. The producing method according to claim 1,wherein a pair of rollers are used in said stretching step, wherein saidfilm is inserted in a gap between said rollers and pressed therein. 6.The producing method according to claim 5, wherein said rollers areheated to a temperature above said shape-providing temperature.